View Sample Alloy Digest Data Sheet (PDF)Since 1952, Alloy Digest has been the leading reference for materials property data on metals and alloys used throughout the world. Featuring graphs, charts and tables, these sheets give facts and figures on composition or characterization, physical and mechanical properties, heat treatment, and machinability.NAK 55 is a very clean steel for use in plastic and rubber molds were impact resistance is not critical in design. Its age-hardening gives very high strength and good wear resistance. Tight tolerance are obtained with consistent expansion and contraction properties.